1. Field of the Invention
The present invention relates to compositions comprising sulfur-containing dispersants. Specifically, the present invention relates to a sulfide phosphor paste composition comprising the sulfur-containing dispersants.
More particularly, the present invention relates to a composition comprising a sulfur-containing dispersant which has a structure containing both a carboxyl group and a thiol group as head groups or a structure containing a thiol or thiophene group as a head group, and a sulfide phosphor paste composition comprising the sulfur-containing dispersant.
2. Description of the Related Art
In recent years, various display devices have been developed and widely used as replacements for cathode ray tubes (CRTs). Such display devices include flat panel displays (FPDs), e.g., liquid crystal displays, plasma display panels, electroluminescence displays and field emission displays, and vacuum fluorescent displays. These display devices necessarily include fluorescent films and thus their luminescent properties are dependent on the physical properties of the fluorescent films.
Sulfide phosphors, such as SrGa2S4, are widely used in the fields of field emission displays and cathodoluminescent displays. Fluorescent films for a variety of display devices are produced by preparing a phosphor paste composition comprising a phosphor, uniformly applying the phosphor paste composition to a given support, and drying the coated support. Representative sulfide phosphor paste compositions are composed of a mixture of a solvent, a binder, and a sulfide phosphor, and optionally comprise a dispersant for improving the dispersibility of the phosphor.
Such sulfide phosphor pastes tend to react with moisture or be chemically unstable in organic solvents (e.g., ethyl cellulose, terpineol and butyl carbitol acetate (BCA)) used in the preparation of the pastes. Some constituent components of sulfide phosphor paste compositions may be completely dissolved in solvents, such as ethyl cellulose, thus deteriorating the luminescent properties of display devices comprising fluorescent films produced from the compositions.
Where the viscosity reduction effect of dispersants in sulfide phosphor pastes is insufficient, the phosphors are inevitably used in relatively small amounts. Conversely, since an increased loading amount of phosphors can cause an increase in the viscosity of sulfide phosphor pastes, the workability of fluorescent films prepared therefrom is poor, e.g., through formation of non-uniform fluorescent films, leading to low yields and low productivity of the fluorescent films.